Making a withdrawal for the upcoming payday? They were soldiers in military uniforms?

Did they seem nervous? Did you notice if their rifles were still on safety? Any sign of struggle or disruption inside?

I don't know how they are doing soldier's pay anymore, in cash or electronically. Transporting official, government money demands security and tight custody control. Six or eight well armed soldiers outside used to be the norm. It would raise eyebrows of tourists in the downtown square many who had never seen automatic weapons before, especially in Mexican tourist zones.

Armored car guards have detailed training and subject to strict hiring selection process. Military is like you say, often young conscripts simply fulfilling their military service obligation so it takes more to provide "needed security". Back during the Chiapas conflict, I slowly became accustomed to being lined on by the side of the bus, held at gun point while identification was checked. The majority of soldiers along the main highways were young guys doing their "military duty" while the real bad asses, the ones that thrived on bloodshed (murder and torture)were back in the jungle. They're mostly not dangerous (I never got confirmation that they actually had bullets in Cozumel), JUST DON'T MAKE ANY SUDDEN MOVES!